The most consistent difference observed between caries-free and caries- susceptible subjects relates to regulation of plaque pH; caries free individuals neutralize plaque acid more effectively. We hypothesize that this difference is related to elevated levels of free dibasic amino acids and arginine/lysine-containing peptides in the saliva of caries-free persons. We will first quantitate levels of individual low molecular weight peptides in parotid saliva collected from mature caries-free and caries- susceptible adults (equal to or more than 50 yrs.). Salivary peptides which are observed to be associated with caries experience will be characterized for their ability to buffer plaque fluid and to yield ammonia when metabolized by oral microorganisms. We will also raise antibodies to the salivary peptides which are associated with caries experience for the purpose of developing immunoassays to quantitate these peptides. We will then determine the levels of these peptides in a group of children who will be examined longitudinally for four years; at each exam, caries status (i.e. caries-free or caries-susceptible) will be determined and parotid salivary peptides and free amino adds quantitated. The identification of salivary factors which are involved in plaque pH regulation will enhance our understanding of host resistance to dental caries.